Switch



May 29, 1962 3,037,103

5. L. BINFORD ETAL SWITCH Filed March 18, 1959 g/g, VI'SNTORSJ AT T ORNEYS'.

3,037,103 Patented May 29, 1962 3,037,103 SWITCH Benjamin L. Binford,Chicago, and Arnold P. Darsch, Evanston, 111., assignors to Magnetrol,Inc., Chicago, Ill., a corporation of Illinois Filed Mar. 18, 1959, Ser.No. 800,245 8 Claims. (Cl. 200-112) This invention relates to switchesand more particularly to magnetically operated switches having snapaction characteristics.

It has heretofore been proposed to operate electric switches forcontrolling or indicating functions in response to movement of amagnetic element which is connected to a sensing device, such as afioat, to be moved thereby. One problem encountered in such switches hasbeen the provision of a snap action effect so that the switch will movepositively to open or closed position and will remain in such positionover a predetermined range of movement of the magnetic element toprovide a high degree of stability. This problem is particularly acutein enclosed mercury type switches wherein the parts are relatively smalland light and are easily moved in response to small magnetic orvibrational forces.

It is accordingly one of the objects of the present invention to providea switch in which a movable contact element is moved to both its openand closed position with a positive snap action and is held in itsexisting position over a predetermined range of movement of theoperating magnetic element.

Another object is to provide a switch of the enclosed mercury type inwhich the movable contact is operated with a positive snap action.

According to one feature of the invention, the movable contact ispivoted to swing toward and away from a fixed contact and carries anelongated magnetic element extending across the pivotal axis to providea positive snap action.

A further object is to provide a switch in which the movable contact ispivotally carried by an elongated fixed contact, both of which projectinto a pool of conductive liquid so that no current is required to passthrough the pivotal mounting of the pivoted contact.

According to one feature of the invention, one of the contacts is madeof a material which is wettable by the conductive liquid and is formedwith capillary passages to maintain it Wet so that its engagement withthe other contact is always made through a film of the conductiveliquid.

A still further object is to provide a switch in which the conductiveliquid is confined to prevent loss of contact due to splashing.

The above and other objects and features of the invention will be morereadily apparent from the following description when read in connectionwith the accompanying drawing, in which:

FIGURE 1 is a central section through a switch assembly embodying theinvention;

FIGURE 2 is a section through the switch itself on the line 22 of FIGURE1;

FIGURE 3 is a transverse section on the line 33 of FIGURE 2, and

FIGURES 4 and 5 are axial sections at right angles to each other of analternative form of switch.

The switch, as shown, is adapted to be operated magnetically by movementof a magnetic piston member connected to an operating rod 11, which mayin turn be connected to sensing means, such as a float or the like, tomove the magnet in accordance with changes in a condition to beindicated or controlled. The piston of magnet 10 is shiftable in a tube12 of non-magnetic mate rial such as brass which extends verticallythrough an enclosing housing 13 in which the switch mechanism iscontained. The housing is closed at its bottom by a closure plate 14, towhich the tube 12 is secured and a connection 15 is provided throughwhich electrical wire can be led into the housing for connection to theswitch.

The tube 12 carries a mounting clip structure 16 which may be formed ofsheet metal with opposite spring arms, one of which is indicated at 17fitting over the tube 12 and resiliently engaging a switch indicatedgenerally at 18 to hold it in position closely adjacent and parallel tothe tube. The spring clip may also carry a terminal block '19 connectedthrough leads 21 to the switch and adapted to be connected to externalleads entering the casing through the connector 15.

The switch 18 comprises an enclosing body 22, of glass or similarnon-conductive material, receiving a pool of conductive liquid 23, suchas mercury. Elongated terminals 24 and 25 extend vertically into thebody in parallel spaced relation to each other with the terminal 24projecting into the pool of mercury 23 and with the terminal 25terminating above the pool of mercury and carrying a transverse contactbar 26. Preferably, the terminals 24 and 25 and the contact bar 26 aremade of a material which will not be wetted by the conductive liquid.For example, when mercury is employed as the conductive liquid, theterminals and contact bar are made of a ferrous material, such as lowcarbon steel or iron.

The terminal 24 pivotally carries a movable contact structure for whichpurpose a U-shaped bracket 27 is secured thereto intermediate its endswith the arms of the bracket projecting horizontally from the terminal.A pivot bearing 28, which may be formed of carbon or the like, isrotatably mounted on one of the arms of the bracket 27 and carries anelongated magnetic element 29, such as an iron plate. The element 29extends vertically across the axis of the pivot 28 and at its lower endcarries a contact member 31 which extends into the conducting liquid 23,and which is movable into and out of contact with the contact "bar 26.

According to one feature of the invention, the contact element 31 ismade of a material which will be wetted by the conducting liquid so thatit will at all times be coated by a film of conductive liquid and willengage the contact bar 26 through a film of conductive liquid to providemaximum contact area and minimum contact resistance. When mercury isused as the conducting liquid, the contact element 31 may be made ofmetal, such as copper, platinum, various alloys, or the like, which willbe wetted easily by the mercury and will carry a film of mercury on itssurface at all times. Preferably, the element 31 is cut out, as shown at32, to provide an arcu-ate surface for maximum area of contact with thecontact bar 26. Preferably, a capillary passage, such as groove 33, isprovided in the element 31, opening into the cut out 32 to maintainmercury on the surface of the cut out at all times.

With the switch mounted, as shown in FIGURE 1, when the magnetic piston10 is centered with respect to the pivotal axis 28, the magnetic forceexerted on the element 29 on opposite sides of the pivot will bebalanced and there is no tendency for the movable contact to move. Ifnew the magnetic piston is moved upward, the magnetic attraction on theupper part of the element 29 will exceed the attraction on the lowerpart and the magnetic element will swing clockwise to move the contactelement 31 into engagement with the contact bar 26 to complete a circuitthrough the switch. It will be noted that this circuit goes from thecontact 24, to the conducting liquid, through the conducting liquid tothe contact element 3 1, from the contact element 31 to the contact bar26 and the contact '25, so that no current is required to be carriedthrough the pivot 28 or the magnetic element 29. Thus, minimum contactresistance is assured for this reason and because of the engagementthrough a film of conducting liquid between the contact element 31 andthe contact bar 26.

As the magnetic piston 10 moves downward and reaches a position where itis symmetrical with respect to the pivot 28, the switch will still beheld in its closed position because the air gap between the upper partof the magnetic strip 29 and the magnet is smaller than the air gapbetween the lower part of the strip 29 and the magnet. As the pistoncontinues to move downward, the magnetic attraction on the lower part ofthe strip 29 will eventually exceed the magnetic attraction on the upperpart of the strip and the strip will swing counter-clockwise to move thecontact element 31 away from the contact bar 26. It will be observedthat this action will ocour rapidly with a snap acting effect since oncethe movement starts the air gap at the upper part of the magneticelement is increasing while that of the lower part thereof isdecreasing. Thus, the movable contact will be moved positively andrapidly from its engaged position to its disengaged position.

Similarly, when the magnetic piston moves upward, the parts will remainin the disengaged position until the magnetic piston has moved above thepivotal axis 28 a predetermined amount, at which time the movablecontact will be moved positively and quickly with a snap actionoperation into switch closing position. Due to this operation,fluttering of the contacts is avoided and the switch operation is highlystable even when it is subject to physical vibrations or is mounted on amoving device.

FIGURES 4 and 5 illustrate an alternative form of switch constructiondesigned particularly for use in locations subject to severe vibrationsor pitching, as on shipboard and the like. Parts in FIGURES 4 and 5corresponding to like parts in FIGURES 1 to 3, are indicated by the samereference numerals, plus 0. In this construction, the tubular body 122is pinched inwardly at opposite sides, as indicated at 135, to leave arelatively narrow, elongated throat extending across the body spacedabove its bottom and slightly above the pool of conductive liquid 123.The fixed contact member 124 may extend through the top of the body andthrough the throat therein but, as shown, is inserted through the bottomof the body into the pool of conductive liquid.

The other fixed contact 125 terminates above the narrow throat in thebody, and at its lower end is offset, as indicated at 125a, to extendtoward the movable contact, as described hereinafter.

The movable contact comprises a trough-shaped element 131, formed of amaterial which will easily be wetted by the conductive liquid, and whichis formed in the side facing the contact element 125a with a grooveextending completely to the bottom of the element 131 and opening intothe pool of conductive liquid. The element 131 may be moved by thearmature 129 in the same way as the element 31 of FIGURES 1 to 3, ormay, if desired, be spring biased in one direction and magneticallyurged in the opposite direction.

In this construction, the grooves in the element 131 will be maintainedsubstantially full of conductive liquid at all times due to thecapillary action. When this element moves to the left, as seen in FIGURE5, the tip portion 125a will enter the groove and contact the conductiveliquid therein to complete a circuit between the contacts 124 and 125through the pool of liquid and the contact element 131. It will be notedthat in this case, as in FIGURES 1 to 3, no current passes through thepivotal mounting for the armature 129 and contact element 131. In allcases, engagement between the fixed contact 125a and the element 131will be made through -a film or pool of conductive liquid so that goodelectrical contact is assured at all times. Furthermore, the making ofcontact through a film of liquid assists in the production of a quickmake and break action, since the liquid will tend to remain inengagement with the fixed contact a, and will break away from itrapidly, as soon as the contact elements are sufliciently separated.

While two embodiments of the invention have been shown and describedherein, it will be understood these are illustrative only and are not tobe taken as a definition of the scope of the invention, reference beinghad for this purpose to the appended claims.

What is claimed is:

1. A switch comprising a pair of elongated fixed spaced contact members,a movable contact pivotally mounted on one of the contact members on anaxis transverse to the length thereof and swingable about said axis intoand out of engagement with the other contact member, an elongatedmagnetic element rigidly secured to the movable contact and extending onopposite sides of said axis transversely thereto, and a complementarymagnetic element movable parallel to the contact members across saidaxis to move the movable contact with a snap action.

2. A switch comprising a non-conducting enclosure, a pair of elongatedvertical contact members in the enclosure in fixed spaced relation toeach other, a movable contact pivotally mounted on one of the contactmembers on a horizontal axis and extending downward from the axis toswing toward and away from the other contact member, a verticallyelongated magnetic element secured to the movable contact and extendingacross the pivotal axis thereof and a complementary magnet movableparallel to the contact members across said axis to move the movablecontact with a snap action.

3. A switch comprising a non-conducting enclosure, a pair of elongatedvertical contact members in the enclosure in fixed spaced relation toeach other, a movable contact pivotally mounted on one of the contactmembers on a horizontal axis and extending downward from the axis toswing toward and away from the other contact member, a pool ofconducting liquid in the enclosure, the movable contact and said one ofthe contact members extending into the pool of conducting liquid and theother contact member terminating above the surface of the pool ofliquid, and a vertically elongated magnetic element secured to themovable contact and extending across the pivotal axis thereof to movethe movable contact toward and into conductive engagement with saidother contact member.

4. A switch comprising a vertical tube of non-magnetic material, amagnetic element movable longitudinally in the tube, an elongatedenclosure of non-conducting material secured to the tube in parallelrelation thereto, a pair of vertical spaced contact members fixedlymounted in the enclosure, a movable contact pivotally mounted on ahorizontal axis on one of the contact members to move toward and awayfrom the other contact member, and a vertically elongated magneticelement secured to the movable contact and crossing its pivotal axis,the magnetic elements being complementary whereby as the first namedelement moves in the tube the second element and the movable contactwill be moved with a snap action.

5. A switch comprising a Vertical tube of non-magnetic material, amagnetic element movable longitudinally in the tube, an elongatedenclosure of non-conducting material secured to the tube in parallelrelation thereto, a pair of vertical spaced contact members fixedlymounted in the enclosure, a movablecontact pivotally mounted on ahorizontal axis on one of the contact members to move toward and awayfrom the other contact member, a pool of conducting liquid in the lowerpart of the enclosure, the movable contact and said one of the contactmembers extending into the conducting liquid and the other contactmember terminating above the pool of liquid, and a vertically elongatedmagnetic element secured to the movable contact and crossing its pivotalaxis, the magnetic elements being complementary whereby as the firstnamed element moves in the tube the second element and the movablecontact will be moved with a snap action.

6. A switch comprising an enclosure of non-conducting material, a poolof conducting liquid in the lower part of the enclosure, a fixed contactin the enclosure extending into the pool of liquid, at second fixedcontact in the enclosure terminating in a contact tip above the pool ofliquid, at contact member mounted for pivotal movement toward and awayfrom the contact tip and projecting into the pool of liquid, the contactmember being formed of a material which is wetted by the liquid andhaving a portion of concave section complementary in section to thecontact tip to fit against the contact tip whereby con tact between thecontact member and contact tip will be through a film of the liquid,

7. A switch comprising an enclosure of non-conducting material, a poolof conducting liquid in the lower part of the enclosure, a fixed contactin the enclosure extending into the pool of liquid, a second fixedcontact in the enclosure terminating in a contact tip above the pool ofliquid, 3. contact member mounted for pivotal movement toward and awayfrom the contact tip and projecting into the pool of liquid, the contactmember being formed of a material which is wetted by the liquid andhaving a portion of concave section complementary in section to thecontact tip to fit against the contact tip, and means defining acapillary passage in the contact member ex tending from below the levelof the pool to the portion of concave section.

8. The switch of claim 6 in which the enclosure is formed with a portionof reduced section above the pool and below the contact tip to limitsplashing of liquid in the enclosure.

References Cited in the file of this patent UNITED STATES PATENTS1,950,178 Hunciker Mar. 6, 1934 2,085,316 Hunciker June 29, 19372,524,261 Kaminky Oct, 3, 1950 2,921,161 Scata et a1. Jan. 12, 1960

